This invention relates to a method of forming patterns upon a dial plate or masking plate of a timepiece, by embossing the dial plate or masking plate with a mold formed by an electroforming process.
The dial plate of a conventional type of timepiece having time indicating hands, or the masking plate of an electronic timepiece of digital display plate is generally made from a material such as brass. In order to render the timepiece more attractive, it is a common practice to form a pattern on the visible surface of the dial plate or masking plate. Conventionally, such a pattern is produced by means of surface treatment with a rotating metal brush, or by transferring a design to the plate by means of electroforming. The method of using a metal brush to from a pattern has the disadvantage that the variety of designs which can be produced is limited, and that rather elaborate facilities are required in order to implement this method on a mass production basis. Use of a plate having a pattern formed thereon by electroforming has the disadvantage that copper is almost the only metal which is suitable for use as the electroforming material, due to economic and other considerations. Since copper is a relatively soft metal, this method makes it difficult to securely weld the legs of the dial plate or masking plate to the body of the timepiece. In addition, due to the complexity of the electroforming process, and the low yield obtained, this process is unsuited to mass production manufacture, so that it is difficult to produce dial plates or masking plates at low cost by this method.
Another method which is sometimes adopted is to directly emboss a pattern from some pattern forming material, such as a layer of small steel balls for example, onto the dial plate surface. However this method is also difficult to implement on a mass production basis, and it is also difficult to secure a high degree of reproducibility of the pattern.